本研究旨在探討日本長期實施低利率與負利率政策環境下，利率降低對銀行獲利能力與風險承擔行為之變化，並分析都市銀行與地區性銀行在該環境下的異質性反應。研究動機來自於日本自1990年代泡沫經濟後進入「失落時代」，實施多項超寬鬆貨幣政策，對以傳統存放款利差為主要收入來源的銀行體系造成深遠衝擊，惟現有文獻對不同類型銀行的行為調整與風險反應仍缺乏系統性探討。
本文以2004年至2023年間之日本都市銀行與地區性銀行為樣本，運用固定效果模型與系統GMM模型進行分析。實證結果顯示，日本銀行在面對低利率環境下，利率水準降低不一定造成利差減少，但負利率政策顯著壓縮銀行獲利，而地區性銀行在利率變動的敏感性大於都市銀行，但該影響在動態調整過程中逐漸被吸收。風險層面方面，無論都市或地區性銀行，在低利率環境下皆有提高風險性資產配置之現象，惟未伴隨信用風險顯著上升，而兩類銀行在風險面對下未展現差異性。本研究驗證低利率政策對銀行行為具有深層影響，並指出銀行類型差異將導致其於獲利面具有調整策略分歧，對未來貨幣政策與金融監理具有重要啟示。

This study investigates the impact of prolonged low and negative interest rate policies on the profitability and risk-taking behavior of Japanese banks, focusing on both city and regional banks. Using annual panel data from 2004 to 2023, we employ fixed effects and system GMM models to estimate the effects of interest rate changes under a low-rate environment on bank behavior. Empirical results from the fixed effects model suggest that banks' net interest margins are not adversely affected. However, negative interest rates significantly compress overall profitability, with regional banks being more sensitive to rate changes. These effects, however, appear to diminish through dynamic adjustment, as revealed by the system GMM model. On the risk side, both city and regional banks increase their holdings of risk-weighted assets in response to prolonged low interest rates, yet without a significant rise in credit risk. Notably, the two types of banks do not exhibit substantial differences in their risk-taking responses, suggesting a convergence in risk behavior under monetary easing. Overall, the study highlights the differentiated profitability responses and the homogeneous risk reactions among bank types under unconventional monetary policy, offering implications for financial regulation and macroprudential supervision.

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